Self-contained propulser with two-degree-of-freedom actuation

ABSTRACT

An invention disclosed herein pertains to a thruster suitable for underwater vehicles. Such a thruster includes a steerable duct and propeller. The thruster motor, the two directional servo motors and all necessary electronics are contained in a single fluid filled and pressure compensated container. This is made possible, by a compact steering mechanism that allows the propeller and duct to be steered about the pitch and yaw axis of the vehicle and a spherical rolling seal which allows the fluid in the thruster to be maintained at a pressure of 2-5 psig. A gimbal that features a ring drive element enables efficient use of space. An actuation to drive the thruster may fit inside the ring drive element.

RELATED DOCUMENT

Priority is hereby claimed to Provisional U.S. Patent Application Ser. No. 60/619,157, filed on Oct. 15, 2004, the entirety of which is hereby incorporated by reference.

BACKGROUND

Underwater vehicles are frequently propelled by means of a single thruster that is pivoted to control the vehicle in pitch and yaw. U.S. Pat. No. 6,572,422 (the contents of which are fully incorporated herein by reference) teaches one such arrangement in which the motor driving the propeller is housed in an oil-filled, water-tight housing that is then pivoted about the pitch and yaw axis by two servomotors that are themselves housed in separate oil-filled, water-tight housings, all controlled by electronics which are themselves mounted in their own oil-filled, water-tight housings. This system requires a large pressure compensator consisting of a pressurized oil reservoir and associated plumbing to accommodate the changes in oil volume due to pressure and temperature variation. This results in a large number of hoses and waterproof cables and connectors and a heavy, bulky assembly.

An object of an invention hereof is to contain the thruster motor, the two servomotors, the electronics, and the pressure compensation in a single oil-filled housing. This results in a smaller, lighter package.

SUMMARY

An invention hereof is directed to a propulser suitable for use in all types of underwater vehicles. Such a propulser contains the means for propelling the vehicle (the thruster), the means for directing the vehicle (the actuators), the means of maintaining an internal pressure slightly greater than the external pressure (the compensators), and the control electronics to drive the thruster motor and the two actuator motors, all housed in a single, pressure housing filled with oil or a similar inert fluid. In addition to several static o-ring seals, such a propulser uses a spherical rolling seal, which allows the thruster to be pivoted about two axes while still maintaining a pressure-tight seal.

The rolling spherical seal is a thin flexible membrane. The main part of the seal is formed as a section of a sphere, approximately symmetrical about its equator. The two ends of the seal are cast in the form of a bead to provide a means of securing the ends of the seal and to provide surfaces to seal against. When installed, the seal is folded back on itself as shown in FIG. 12. The center of rotation of the thruster should preferably correspond to the center of the spherical section of the seal.

BRIEF DESCRIPTION OF FIGURES

FIG. 1 is an isometric view of a generic underwater vehicle and defines Pitch and Yaw axes for reference below.

FIG. 2 shows a complete thruster assembly 2 with a stator 4 and a propeller 6 in place. One of two pressure compensator assemblies 8 is shown. The thruster assembly 2 is symmetrical, so it will be understood that there is another compensator assembly 8 on the opposite side of the thruster assembly 2.

FIG. 3 shows the thruster assembly 2 with the stator 4 and the propeller 6 removed for clarity. It also shows the orientation of the two section views, A-A and B-B.

FIG. 4 shows SECTION B-B of the thruster assembly 2. This section passes through the pressure compensator assemblies 8.

FIG. 5 shows SECTION A-A of the thruster assembly 2.

FIG. 6 shows a mechanism to rotate the thruster about the pitch and yaw axis, with a pressure vessel 16, compensator assemblies 8, and all other components not required to move the thruster, removed for clarity.

FIG. 6A shows a gimbal assembly in side view and section view.

FIG. 7 shows an actuator group deflected fully to the right, about the yaw axis (approximately 21 degrees), clockwise as viewed from above.

FIG. 8 shows the actuator group deflected fully to the left, about the yaw axis (approximately 21 degrees), counterclockwise as viewed from above.

FIG. 9 shows the actuator group deflected fully up, about the pitch axis (approximately 21 degrees), clockwise as viewed from the right.

FIG. 10 shows the actuator group deflected fully down, about the pitch axis (approximately 21 degrees), counterclockwise as viewed from the right.

FIG. 11 shows a rolling spherical seal 26, as it rotates from −16 degrees to +16 degrees.

FIG. 12 shows the rolling spherical seal 26 in section view, as it rotates from −16 degrees to +16 degrees.

FIG. 13 shows the thruster assembly with the thruster 28 deflected down 16 degrees.

FIG. 14 shows the rolling seal in its unfolded condition.

FIG. 15 shows the folded rolling seal in cross-section.

FIG. 16 illustrates a spur-bevel gear assembly.

DESCRIPTION

Underwater vehicles need to propel themselves and control their direction of travel. A common configuration for underwater vehicles is shown in FIG. 1. A thruster assembly 2 can be pivoted to control the vehicle in pitch and yaw defined in FIG. 1.

FIG. 2 illustrates the thruster assembly 2. Propulsion is provided by means of a non-rotating duct 4, containing a propeller 6. The mechanical and electrical components of the thruster 2 are contained in a pressure-tight housing 16 which is filled with an incompressible, non-conducting, non-corrosive fluid, such as mineral oil. The fluid is maintained at a pressure approximately 2-5 psi higher than the pressure of the surrounding fluid by a pair of pressure compensators 8.

FIG. 3 illustrates the thruster assembly 2 with the duct 4 and propeller 6 removed for clarity. Referring to FIG. 3, FIG. 4, FIG. 5, FIG. 6, and FIG. 6A the thruster assembly 2 consists of a baseplate 30 to which is rigidly mounted a trunnion mount 40. The trunnion mount 40 supports servo motor assemblies 50A and 50B. The trunnion mount 40 also supports spur-bevel gear assemblies 46A and 46B through trunnion pins 44A and 44B on bearings 42A and 42B.

The spur-bevel gear assemblies 46A and 46B support a gimbal 39 through the bearings 32A and 32B. The gimbal assembly 39 supports a forward pressure housing 14 through forward pressure housing supports 24A and 24B, which rotate on bearings 32A and 32B. The forward pressure housing 14 supports the duct 4. The forward pressure housing 14 also supports the thruster motor gearbox assembly 28. The thruster motor-gearbox assembly 28 supports the propeller 6.

The bearings 42A, 42B, 32A, and 32B allow the forward pressure housing 14 and all components supported by it to rotate about the pitch and yaw axes. This rotation is controlled by a gear train that starts with spur gears 48A and 48B of servo-motor assemblies 50A and 50B. These spur gears drive the spur-bevel gear assemblies 46A and 46B, see FIG. 16. A spur gear 47 is rigidly attached to a yaw bevel gear 49 and rotates on bearing 32. A yaw bevel gear 49 on each of the spur-bevel gear assemblies 46A and 46B meshes with a ring bevel gear 20. The ring bevel gear 20 is supported by the gimbal 39 through a ring bevel gear support 36 which rotates on a bearing 38.

The ring bevel gear 20 also meshes with a pitch bevel gear 22. The pitch bevel gear is rigidly attached to the forward pressure housing support 24A, which, as already discussed, supports the forward pressure housing 14, so that the forward pressure housing 14 will move with the forward pressure housing support 24A.

FIG. 6, FIG. 6A, FIG. 7, FIG. 8, FIG. 9, and FIG. 10 illustrate the operation of the directional control of the thruster assembly 2. The forward pressure housing 14 and the thruster motor gearbox assembly 28 are omitted from these views for clarity. However, it is understood that the forward pressure housing 14 and therefore the thruster motor gearbox assembly 28 will move with the forward pressure housing supports 24A and 24B.

When the spur gears 48A and 48B drive the spur gears 47A and 47B in the same direction as each other, as illustrated in FIG. 7 and FIG. 8, two yaw bevel gears 49A and 49B will bear equally against the ring bevel gear 20. The ring bevel gear 20 is unable to rotate about its own axis and therefore acts through the ring bevel gear support 36 and bearing 38 to rotate the gimbal assembly 31 around the yaw axis.

When the spur gears 48A and 48B drive the spur gears 47A and 47B in opposite directions, from each other, as depicted in FIG. 9 and FIG. 10, the yaw bevel gears 49A and 49B act on the ring bevel gear 20 in opposite directions. This will cause the ring bevel gear 20 to rotate about its own axis. The ring bevel gear 20 will then drive the pitch bevel gear 22 which will in turn rotate the forward pressure housing support 24B about the pitch axis.

By driving the spur gears 47A and 47B by differing rotational amounts, any combination of rotations about the pitch and yaw axis is possible, within the mechanical limits of the device. Also, the orientation of the thruster assembly 2 is somewhat arbitrary and the thruster assembly 2 may be rotated so that the axis labeled yaw and pitch may point in any direction.

Another feature that is important to the function of the thruster assembly 2 is the rolling spherical seal 26. The rolling spherical seal 26 is illustrated in an unfolded configuration in FIG. 14. The seal 26 is constructed of a flexible, waterproof material such as urethane or silicon. FIG. 14 shows the shape of the seal “as cast”. FIG. 15 provides a section view of the seal 26 in the unfolded configuration. The seal 26 consists of an outer bead 26A, an inner bead 26B, and a connecting skirt 26C. The connecting skirt 26C is roughly spherical in cross-sections as shown in FIG. 15. Angles E1 and E2 are approximately equal. The inner radius of the seal 26, RI, is approximately equal to the outer radius of the forward pressure housing 14.

For a representative embodiment having a pressure housing that is approximately 9.5 in. (241.3 mm) long, with an oil volume of about 50 in³ (819 cm³), a silicone seal of 0.031 in. (0.787 mm) thick is reasonable. The pressure across such a seal can be approximately 3 psi. The seal gap can be on the order of between 0.09-0.125 in (2.3-3.18 mm). A reasonable motor to use for the servo motors 50A and 50B is available from MicroMo Electronics, Inc. of Clearwater, Fla., a member of the Faulhaber Group, 2444 motor series 30/1 415:1 reduction. A suitable thruster motor is available from AVEOX of Simi Valley, Calif., model 1817, combined with model 017P 10:1 planetary gearbox available from CGI, Inc., of Carson City, Nev. The deflection of the propeller and duct about the pitch and yaw axes is approximately ±15°.

On installation, the outer bead 26A is rolled back 90° and the seal is folded back on itself. When the seal 26 is at 0° deflection, i.e. the outer bead 26A is parallel to the inner bead 26B, the fold of the seal 26 is at approximately the equator of the spherical connecting skirt 26C. The seal in its installed shape is shown in FIG. 11 and in cross section in FIG. 12. These figures also illustrate how the seal changes shape as it is rolled from −16° to +16°.

FIG. 13 shows the rolling spherical seal 26 installed in the thruster assembly 2. The outer bead 26A is trapped between the sealing ring 18 and the forward sealing ring 10. The inner bead 26B is trapped between a pressure housing clamping ring 34 and the forward pressure housing 14. The connecting skirt 26C is supported by the forward sealing ring 10 and the seal fairing 12 outboard and by the forward pressure housing 14 inboard. The internal pressure of the thruster assembly 2 helps maintain the shape of the seal. The sealing ring 18 has a small lip that both traps the outer bead 26A and helps push the skirt against the forward sealing ring 10, thereby preventing the seal from bulging out. In operation, the seal rolls back and forth between the forward sealing ring 10 and the seal fairing 12 outboard and the forward pressure housing 14 inboard as the pressure housing 14 rotates about the pitch and yaw axis either individually or in any combination of the two.

Many techniques and aspects of the inventions have been described herein. The person skilled in the art will understand that many of these techniques can be used with other disclosed techniques, even if they have not been described as being used together. Thus, the fact that a sub-combination of features that are described separately, may not be described in sub-combination, does not mean that the inventor does not regard any such sub-combination as an invention that is disclosed herein.

This disclosure describes and discloses more than one invention. The inventions are set forth in the claims of this and related documents, not only as filed, but also as developed during prosecution of any patent application based on this disclosure. The inventor intends to claim the various inventions to the limits permitted by the prior art, as it is subsequently determined to be. No feature described herein is essential to each invention disclosed herein. Thus, the inventor intends that no features described herein, but not claimed in any particular claim of any patent based on this disclosure, should be incorporated into any such claim.

An abstract is submitted herewith. It is emphasized that this abstract is being provided to comply with the rule requiring an abstract that will allow examiners and other searchers to quickly ascertain the subject matter of the technical disclosure. It is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims, as promised by the Patent Office's rule.

The foregoing discussion should be understood as illustrative and should not be considered to be limiting in any sense. While the inventions have been particularly shown and described with references to preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the inventions as defined by the claims.

The corresponding structures, materials, acts and equivalents of all means or step plus function elements in the claims below are intended to include any structure, material, or acts for performing the functions in combination with other claimed elements as specifically claimed. 

1. A seal member comprising a flexible membrane comprising a substantially symmetrical section of a spherical surface.
 2. The seal member of claim 1, the section of a spherical surface comprising an inner end having an inner radius, coupled by a skirt to an outer end, having an outer radius that is larger than the inner radius.
 3. The seal member of claim 2, at least one of the inner and outer ends of the seal member comprising a bead.
 4. The seal member of claim 1, the flexible membrane consisting essentially of a material selected from the group of urethane and silicone.
 5. The seal member of claim 1, the flexible membrane comprising an extent between the inner and outer end of a spherical arc of slightly more then one half the maximum deflection of a joint in which the seal member seals.
 6. The seal member of claim 1, the membrane having a flexibility and thickness such that the membrane is foldable upon itself so as to align the inner and the outer ends to be concentric with each other.
 7. The seal member of claim 1, further comprising: a. an inner housing member, having an outer edge, sized to couple with the inner end of the spherical section; and b. an outer housing member, having an inner edge sized to couple with the outer end of the spherical section.
 8. The seal member of claim 1, the membrane having a strength capable of maintaining a seal against a relative pressure across it of between one and five pounds per square inch.
 9. The seal member of claim 7, further having a flexibility such that, starting from a 0° position in which the inner and outer ends of the seal are concentric, the outer end is rotatable, relative to the inner end, around two orthogonal axes that are coincident in the 0° position with diameters of both ends of the seal member.
 10. The seal member of claim 9, the two orthogonal axes comprising yaw and pitch axes of a vehicle, of which the housing members are a component.
 11. A vessel comprising: a. an outer housing member having a spherical inner surface; b. an inner housing member having a spherical outer surface, located with the outer surface of the inner housing member concentric with, spaced from, and inside the inner surface of the outer housing member; and c. spanning from the inner surface of the outer housing member to the outer surface of the inner housing member, a flexible seal member comprising a membrane that is a substantially symmetrical section of a spherical surface.
 12. The vessel of claim 11, further wherein the section of a spherical surface of the seal comprises an inner end having an inner circumference, coupled by a skirt to an outer end, having an outer circumference that is stretched to be larger than the inner circumference.
 13. The vessel of claim 11, the inner end of the spherical surface of the seal member being coupled to the inner housing member and the outer end of the spherical surface of the seal member being coupled to the outer housing member, and the skirt being folded.
 14. A vessel comprising: a. an inner housing having a first portion; b. an outer housing having a first portion, concentric with and at least in part surrounding the first portion of the inner housing; and c. coupled to both the inner and the outer housings, a spherical section rollable seal member.
 15. The vessel of claim 14, the first portion of the inner housing comprising a section of a sphere having a center and an inner housing circumference, and the first portion of the outer housing comprising a section of a sphere having a center and an outer housing circumference, that is larger than the inner housing circumference.
 16. The vessel of claim 15, the seal being coupled to the inner housing at an inner end and to the outer housing at an outer end.
 17. The vessel of claim 16, the seal arranged relative to the inner and outer housings such that in a 0° position, the seal member is folded, such that the inner and outer ends of the seal member are substantially adjacent each other.
 18. The vessel of claim 16, the folded seal member defining a concave surface and a convex surface at its fold, the concave surface being closer to the inner and outer ends of the seal member than is the convex surface, when the seal member is in a 0° position.
 19. The vessel of claim 14, the inner and outer housings and seal member being arranged such that rotation of the inner housing relative to the outer housing about a first axis that passes through: a. the center of the section of the sphere of the spherical portion of the inner housing; b. the center of the section of the sphere of the spherical portion of the outer housing; and c. the seal equator; causes the seal to roll along itself so that an extent of a different region of overlap of the seal member changes.
 20. The vessel of claim 19, the inner and outer housings and seal member being arranged such that rotation of the inner housing relative to the outer housing about a second axis, that is perpendicular to the first axis and that passes through: a. the center of the section of the sphere of the spherical portion of the inner housing; b. the center of the section of the sphere of the spherical portion of the outer housing; and c. the seal equator; causes the seal to roll along itself so that a different extent of a region of overlap of the seal member changes.
 21. The vessel of claim 20, the inner and outer housings and seal member being arranged such that the inner housing is rotatable relative to the outer housing simultaneously about both the first and second axes without disrupting sealing integrity of the seal.
 22. The vessel of claim 14, there being a region inside the vessel adjacent the concave surface of the sealing member that is pressureizeable to a relatively higher pressure than a region adjacent the convex surface of the sealing member.
 23. The vessel of claim 22, further comprising a pressure compensator that couples the relatively higher pressure region of the vessel to an ambient environment outside of the vessel, such that pressure in the higher pressure region exceeds that of the ambient environment.
 24. The vessel of claim 14, further comprising a pressure compensator that hydraulically couples a relatively higher pressure region of the vessel to an ambient environment outside of the vessel, such that pressure in the higher pressure region exceeds that of the ambient environment by an amount within a set range, and further comprising, within the higher pressure compensated region: a. a first actuator that is coupled to the inner housing; b. a second actuator that is coupled to the inner housing; c. electronic components that provide inputs to the first and second actuators.
 25. The vessel of claim 24, the first actuator comprising a servo-motor.
 26. The vessel of claim 24, the first and second actuators being coupled to a gimbal assembly that is movable with respect to a first and a second degree of freedom.
 27. The vessel of claim 26, the first actuator being coupled to the gimbal assembly to actuate motion of the inner housing with respect to the first degree of freedom.
 28. The vessel of claim 26, the second actuator being coupled to the gimbal assembly to actuate motion of the inner housing with respect to the second degree of freedom.
 29. The vessel of claim 26, the first and second actuators being coupled to the gimbal assembly to independently actuate motion of the inner housing with respect the first and second degrees of freedom. 30-47. (canceled) 